1. Field of the Invention
The invention relates to a process for checking the integrity of a nonporous flexible bag with gusset(s) in order to detect the presence of leaks, and a device for checking integrity for the implementation of this process. The invention likewise relates to bags that have been checked by said process or by means of said device.
The invention is especially intended for disposable sterile bags for bio-pharmaceutical fluids. In this case, high value-added products could be placed in the bags, for which it is critical that it is certain that the bag be tight.
2. Description of the Related Art
Flexible and nonporous bags with two large walls directly joined to one another have been known for a long time. Of these bags, once unfolded, they remain relatively thin; this justifies their often being called “pillow” bags or “2D” bags (D indicating dimensions).
The document FR-A-2 781 202 describes a bag with two large walls and two lateral gussets. Each gusset comprises two small walls connected to one another by an internal fold, and each small wall is connected to the adjacent large wall by an external fold. Such a bag, once unfolded, assumes a three-dimensional shape (cylindrical, prismatic, parallelepipedic . . . ) and can have a volume of 50 liters, or even more; this justifies its being called a 3D bag.
In numerous technical fields and especially in the field of health, it is critical to ensure that fabricated, nonporous flexible bags are tight, i.e., at least have a degree of tightness considered satisfactory. This is even more important in the case in which the bag comprises, following its production, welding lines that can also comprise leak sources.
There are several processes for checking the integrity of such bags.
Standard F 2095-01 of ASTM International entitled “Standard Test Methods for Pressure Decay Leak Test for Nonporous Flexible Packages With and Without Restraining Plates” relates more accurately to the so-called pressure decay process.
This process is envisioned according to two possible embodiments: with restraining plates or without such plates.
In the embodiment with restraining plates, the process is as follows:                in a preparation phase:                    there is a bag to be checked with at least one port that can be blocked or connected in a tight and stationary manner;            there is a source of pressurized gas intended to be introduced into the bag via the port,            there are means for measuring the pressure of the gas in the bag via the port,            there are two fixed restraining plates spaced apart and facing one another, able to not conceal a possible leak in the large walls of the bag placed against them,            the bag is placed flat between the two restraining plates,            at least one port of the bag is connected to the gas source and pressure measurement means so as to be able to send the gas under pressure into the bag and to measure the gas pressure in the bag,                        and, in a final test phase:                    the gas is sent under pressure into the bag, expansion of the bag being limited when its large walls move against the restraining plates,            then, in a final stage, the pressure drop in the bag is compared by the pressure measurement means to a predefined pressure drop threshold of a bag considered tight.                        
If the pressure drop in the bag is less than the threshold, it is considered that the bag has passed the integrity test, whereas if the pressure drop in the bag exceeds the threshold, the bag is considered to not have passed the integrity test. Actually, in this case, the magnitude of the pressure drop is dictated by the presence of one or more leaks.
The embodiment with restraining plates has two advantages over the embodiment without such plates: limiting the volume of the pressurized bag, this increasing the sensitivity of the test, and increasing the internal pressure of the bag. This embodiment, moreover, makes it possible to test the integrity of the peripheral weld that connects the two walls of a 2D bag and the tightness of the port.
In this case, the restraining plates are spaced slightly apart.
Devices are known for implementing a checking process for filters and membranes by the pressure decay technique (but without restraining plates), for example the SARTOCHECK® 4 device from the SARTORIUS Company. Devices with plates are also available from other manufacturers.
In these devices, the restraining plates have the characteristic according to which, in full or in part, for their surface intended to be in contact with a large wall of the bag, they allow passage of pressurized gas originating from the bag if the latter has one or more leaks. For this purpose, and in one embodiment, the restraining plates comprise a porous or similar layer against which the large walls of the bag are placed.
This structural arrangement is critical. Actually, failing this, the plates would block any leakage source against which they would be applied; this would lead to what could be called a “blocked pore” effect. In this case, the pressure drop in the bag established during the check would be less than a predefined threshold, the pore forming the leak being plugged, and this constant could be interpreted as meaning that the bag has passed the integrity check, whereas it in fact has one (or more) leak(s).
The implementation of a tightness test without the restraining plates would make it possible to eliminate the risks of blockage of the pores. Nevertheless, this implementation would lead to continuous expansion of the flexible bag and ultimately to its failure.
The process and device for checking integrity with restraining plates is satisfactory in the case of the “pillow” or “2D” bags described above. Conversely, this process and this device cannot be used in the case of 3D bags because the small walls of the gussets will come to rest against one another due to the short distance between the restraining plates and due to the pressure in the bag. Use of restraining plates with large spacing is not desirable because it would lead to expansion and unfolding of the bag. It will then be necessary to re-fold this bag before its packaging that would adversely affect the speed and ease of implementation of the method.
Of course, implementing processes for checking the integrity of such bags other than the pressure decay process would be possible. This would be at the cost of the advantages of this process, however, specifically its promptness, its ease of implementation, and its capacity to be performed “on line.”
The document US 2006/0277975 describes a test process in which a test material is applied to the bag to be tested, and at least one test is conducted on the layer of the material that has been applied to determine the integrity of the bag.
The tester BT-1000 from the Rycobelgroup Company tests integrity by the pressure decay method.
The document WO 91/16611 describes a bag tester, the bag to be tested being placed between two plates.